Dysexecutive syndrome in schizophrenia: A cross-cultural

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Dysexecutive syndrome in schizophrenia: Across-cultural comparison between Japaneseand British patients

H. Iharaa,∗, G.E. Berriosa and P.J. McKennab

aDepartment of Psychiatry, University of Cambridge,Hills Road, Cambridge, UKbCambridge Psychiatric Rehabilitation Service,Fulbourn Hospital, Cambridge, UK

This study tested the hypothesis that the dysexecutive syn-drome of schizophrenia is impervious to cultural differences.18 Japanese and 22 British patients and 14 Japanese and 19British control subjects were compared on the BADS (Be-havioural Assessment of Dysexecutive Syndrome), a com-prehensive neuropsychological assessment battery, designedfor ‘ecological validity’, and other measures of frontal exec-utive functions (EFs). Both cultural groups of schizophrenicpatients showed equally severe impairment in most executivetests including the BADS (verbal fluency and intelligencewere less impaired). Irrespective of cultural origin, simi-lar neuropsychological deficits were found in patients withminimal intellectual deterioration. Our study suggests thatsocio-cultural background does not affect the dysexecutiveprofile of schizophrenia very much, and that neuropsycho-logical assessment may possibly provide added clinical in-formation relevant to the management and rehabilitation ofschizophrenic patients across different cultures.

Keywords: Cognitive dysfunction, dysexecutive syndrome,cross-cultural study, Japanese

1. Introduction

There has been less empirical research to ascertainthe influence of cultural context on the cognitive disor-ders that accompany schizophrenia than there has beeninto its influence on the rest of schizophrenic symp-

∗Corresponding author / Present address: H. Ihara, National SouthHanamaki Hospital, Suwa 500, Hanamaki, Iwate, Japan 025-0033.Tel.: +81 198 24 0511; Fax: +81 198 24 1721; E-mail: [email protected].

tomatology. Indeed, work in the latter area startedearly [28,40] and the view is still accepted that thesymptoms, course and outcome of schizophrenia areless severe in non-western countries or non-Caucasianethnic groups [6,8,32]. WHO studies [58] have alsofound that culture seems to influence the profile of pos-itive symptoms such as delusion of control, persecutorydelusion, characteristic auditory hallucinations, anddistortions of self-perception. It has also been reportedthat Japanese subjects suffering from schizophrenia aremore self-contained, reclusive, emotionally shallow,and socially withdrawn compared with non-Japanesepatients [16,24,49].

However, as Murphy [39] has pointed out, suchsymptoms may not be relevant to the illness process,and hence their nature and duration are unlikely tomatter much from a neurobiological viewpoint. Thisis because such highly noticeable characteristics yieldto less marked but persistent developments of perva-sive deterioration in distinguishing schizophrenia fromother psychoses. After exacerbation and remission ofdelusions and hallucinations, a considerable proportionof patients fall into a state of severe deterioration withprominent cognitive deficits such as lack of spontane-ity, blunted affect, marked lethargy, loss of forwardplanning and difficulty with abstract thinking.

These cognitive deficits are more or less synony-mous with what, in neuropsychology, has recently beencalled the ‘dysexecutive syndrome’ (DES) [3]. Thissyndrome refers to the impairment of executive func-tions (EFs) whose putative anatomical substrata are thefrontal lobes and basal ganglia. Over the past decade,EFs have become an important field of research inschizophrenia [4,18–21,31,33,43,50,51]. It is claimedthat the dysfunction of EFs in schizophrenia is dispro-portionate to the overall level of the other domains ofhigher brain function [10,15,17,27,56]. To cliniciansworking in rehabilitation settings, these symptoms areof primary concern, as they impede recovery. An un-

Behavioural Neurology 12 (2000) 209–220ISSN 0953-4180 / $8.00 2000, IOS Press. All rights reserved

210 H. Ihara et al. / Cross-cultural study of cognitive function

resolved question is whether culture modifies dysexec-utive patterns. If it did not, the view that schizophre-nia is the same neurobiological disorder across culturesand that DES may be its basic psychopathology will bereinforced.

The comparison of Japan with Britain is germane forthe following reasons. Firstly, the two cultures havedifferent historical traditions and national traits. Japanremains under the influence of a Confucianism char-acterised by family-centricity, socio-centricity and col-lectivism. Britain is an example of a Western societythat emphasises individualism, independence and self-reliance. In this regard, differences in thematic con-tent for positive symptoms between Japanese and Cau-casian schizophrenic patients have been reported [16,24,49]. Secondly, the Japanese language differs fromthe most Indo-European languages in the following re-spect: there are two character systems that comprise theJapanese language, one of them consisting of a largenumber of complex pictorial characters. Due to thepossibility that such complex pictorial characters areprocessed in a different manner from that associatedwith phonemic characters, long-term exposure to thiscognitive-linguistic environment may produce somesorts of neuropsychological variations, such as greaterrelative right hemisphere activation [22,37]. Thirdly,both countries are industrialised, urbanised and liter-ate, so that potentially confounding factors such as dif-ferences in education, intelligence and verbal capacitymay be less of a problem.

This study was designed to investigate the extent andvariation of the dysexecutive syndrome in both culturalgroups. Its aim is to clarify whether patients from bothcultures perform differently on tests of verbal fluency,mental-set shifting, abstract concept formation, goal-directedness and planning and whether level of intelli-gence is a factor in their performance (e.g. [10,51]).

2. Methods

2.1. Participants

A total of 73 subjects participated in this study: 18Japanese schizophrenic patients; 22 British schizophrenicpatients; 14 Japanese and 19 British healthy volunteercomparison subjects.

The Japanese patients with schizophrenia who par-ticipated in this study were recruited from Muroi Hospi-tal, Oyama Fujimidai Hospital and Nasu Hillside Hos-pital, all of which lie in Tochigi Prefecture, Japan, ap-

proximately 100 km north of Tokyo. All the Japanesepatients were being treated with neuroleptics at the timeof the neuropsychological assessment.

The British patients with schizophrenia who tookpart in the study were recruited from a psychiatric re-habilitation service in Cambridge. They were all Cau-casians and native English speakers. Their scores on theNART [42] and the duration and type of their educationindicated that they were considered to be of averagepremorbid intelligence. All were taking neuroleptics.

Semi-structured diagnostic interviews revealed thatall Japanese and British patients met the criteria forschizophrenia according to the Diagnostic and Statisti-cal Manual of Mental Disorders: Fourth Edition (DSM-IV) [2] and the International Classification of Diseases(ICD-10) [59]. Patients with any co-morbidity of othermental illnesses or a history of electroconvulsive ther-apy within the last two years were excluded. For thosewho were taking anticholinergic agents, doses werebelow the level affecting memory test performancein schizophrenia, i.e. the range 5–15 mg procycli-dine daily [52]. Symptomatological evaluations for theschizophrenic groups were made according to semi-structured clinical interviews and standardised ratingscales for the Positive and Negative Syndrome Scale(PANSS) [25] by an English speaking Japanese psychi-atrist (H.I.) and using the patients’ case records. Wefound no difference in symptomatology rated by thePANSS and the neuroleptic dose of chlorpromazineequivalents [11,26] in the two groups with schizophre-nia (Table 2).

Nineteen British control subjects responded to adver-tisements for paid volunteers at the Medical ResearchCouncil Cognition and Brain Sciences Unit,Cambridgeand co-operated in obtaining norms of each neuropsy-chological test. The British patients with schizophreniaand the British control subjects were matched for dura-tion of education and NART-based estimated premor-bid intelligence. Fourteen Japanese control subjects,including housewives, cleaners, farmers and students,were selected to match the other groups for age. Mostof them were paid volunteers recruited by advertise-ment in the local community. We found no signifi-cant statistical age differences among the four groups(F = 2.07, df = 3, 69, p = 0.112). All subjects werescreened for a history of head injury followed by lossof consciousness, substance abuse and general somaticconditions that might affect neuropsychological perfor-mance. We excluded those who had been previouslydiagnosed as learning disorders and met the criteria ofmental retardation and learning disorders, according to

H. Ihara et al. / Cross-cultural study of cognitive function 211

Table 1Demographic and baseline variables of the Japanese schizophrenic patients, the British schizophrenic patients, andthe Japanese and British healthy control subjects (means and, in parenthesis, standard deviations for age, durationof illness, duration of education, and NART-IQ)

Japanese Schizophrenic British Schizophrenic Japanese Control British ControlPatients Patients Subjects Subjects

N 18 22 14 19Female: male 10: 8 7: 15 9: 5 17: 2Age 44.2 (10.6) 37.0 (9.5) 38.4 (12.3) 43.4 (11.2)Duration of illness 17.8 (10.6) 14.1 (8.9)Inpatients: outpatients 17: 1 11: 11Duration of education 12.3 (2.5) 12.0 (2.2)NART-IQ 104.4 (13.8) 103.2 (6.1)

Note.NART = National Adult Reading Test [42].

Table 2The symptoms rated by Positive and Negative Syndrome Scale [25] and the neuroleptic dose of chlorpromazineequivalents in the Japanese and British schizophrenic patients. (means and, in parenthesis, standard deviations)

Japanese Schizophrenic patients British Schizophrenic patients

Positive syndrome 15.5 (5.8) 17.1 (5.2)Negative syndrome 20.7 (4.5) 22.8 (6.3)Composite index − 5.2 (6.1) − 5.7 (6.5)General psychopathology 34.3 (10.3) 41.1 (10.0)Anergia 9.6 (2.7) 11.4 (3.7)Thought disturbance 9.6 (4.0) 10.3 (3.4)Activation 6.4 (2.4) 7.6 (2.8)Paranoid/belligerence 5.4 (2.1) 6.5 (1.9)Depression 6.9 (2.5) 8.2 (3.1)Neuroleptics (= Chlorpromazine) (mg/day) 625.0 (535.6) 608.1 (473.5)

DSM-IV, at the time of the neuropsychological assess-ment.

In order to test the DES hypothesis of schizophrenia,the possibility that the subject’s poor performance onexecutive tests merely reflects low intellectual function-ing must be discounted. For this purpose, we matchedthe four samples for the means of either pre-morbid orcurrent intelligence. For the British schizophrenic sam-ple, we excluded subjects whose mother tongue wasnot English, who could not perform the tests, who wereeither uncooperative or emotionally unstable, and thosewhose National Adult Reading Test (NART) [42] IQwas < 84. The British control sample (normals) wasselected to match the British schizophrenic patients forthe means of duration of education and NART-basedpremorbid IQ. Japanese schizophrenic patients werealso selected to match the British schizophrenic sam-ple on the basis of equivalent average scores on theRaven Advanced Progressive Matrices (RAPM) [46],and also duration of education and duration of illness.The RAPM seems less susceptible to cultural factorsthan other tests such as the Wechsler Adult Intelli-gent Scale [55] and NART [23]. We also deliberatelymatched British and Japanese control subjects on thebasis of RAPM-base current intelligence when recruit-ing the latter control subjects.

Table 1 provides demographic and baseline vari-ables of the Japanese schizophrenic patients, Britishschizophrenic patients, and healthy control subjects.

We obtained a written form of consent from all ofthe participants after the procedure had been fully ex-plained. We also obtained ethical approval from boththe Cambridge Local Research Ethics Committee andthe Clinical Management Committee of each Japanesehospital.

2.2. Methods

The extended battery of neuropsychological tests ofEFs applied to all three groups included: Verbal Flu-ency Test (VFT) [35]; Trail Making Test (TMT) [47];Modified Wisconsin Card Sorting Test (MCST) [41];Stroop Colour Word Test (SCW) [53]; Goal NeglectTest (GNT) [14]; Behavioural Assessment of Dysexec-utive Syndrome (BADS) [57]. General details of theGNT and the BADS are provided here. In terms of theother tests, we have given a brief account of their ap-plication to Japanese subjects, since a full explanationwould be unnecessary due to their clinical popularity.More detailed descriptions can be obtained from the lit-erature shown above. Table 3 shows cognitive domainsassessed by the neuropsychological test battery.


Table 3Cognitive domains examined by the neuropsychological test battery

Cognitive Domain Neuropsychological Tests

IntelligenceNART Estimated premorbid intelligenceRAPM Current intelligence, fluid intelligenceFormal Executive FunctionsVFT Initiation and fluency of speechTMT: B-A Visuo-motor tracking and mental ‘set-shifting’MCST Abstract concept formationSCW Inhibitory control of habitual behaviourGNT Retention of goal-directed mental-setEveryday Executive FunctionsRule Shift Cards Inhibition of pre-learned behaviourAction Programme Development of an action planKey Search Strategy-formingTemporal Judgement Stepwise temporal estimationZoo Map Forward planningModified Six Elements Planning and organisation of behaviourBADS Total Score Everyday executive functions

Note. NART = National Adult Reading Test [42]; RAPM = Raven AdvancedProgressive Matrices [46]; VFT = Verbal Fluency Test [36]; TMT = Trail MakingTest [47]; MCST = Modified Card Sorting Test [41]; SCW = Stroop Colour WordTest [53]; GNT = Goal Neglect Test [14]; BADS = Behavioural Assessment ofDysexecutive Syndrome [57].

2.2.1. Verbal Fluency Test (VFT)This test asks subjects to produce orally as many

words as possible beginning with a particular letter insixty seconds. In this project, the initial letters ‘F’, ‘A’and ‘S’ are used for British subjects, whereas letters‘H’, ‘A’ and ‘S’ are applied to Japanese individuals.The rationale for comparison between English VFT andits Japanese equivalent is provided by the following:the total number of words starting with the letter ‘F’,‘A’ or ‘S’ comprise 23.1% of the entire English vocab-ulary (F: 4.9%; A: 5.3%; S: 12.9%) (Oxford EnglishDictionary), whereas the total number of words begin-ning with the letter ‘H’, ‘A’ or ‘S’ account for 26.3%of the whole Japanese vocabulary (H: 9.8%; A: 3.2%;S: 13.3%) (Shinchosha Modern Japanese Dictionary).We used the total number of all correct words, producedby subjects, as their score.

2.2.2. Trail Making Test (TMT)All subjects performed both Parts A and B of the

TMT. For Japanese subjects, Hiragana characters areused in Part B, according to the dictionary arrangementof the Japanese syllabary. Each Japanese characteris placed on the corresponding letter from the Romanalphabet in the correct order. For example, the firstHiragana character ‘ ’ (pronunciation: short ‘a’) isplaced exactly in the same place as ‘A’, and the secondletter ‘ ’ (pronunciation: short ‘i’) in the same placeas ‘B’. The time taken for Part B subtracted from thetime taken for Part A was scored. A standardised score

based on control means and standardised deviation ismultiplied by ‘−1’ in order to equalise the valence ofstandardised scores on the TMT with the other tests:the lower the score, the greater the impairment.

2.2.3. Modified Wisconsin Card Sorting Test (MCST)This study applied Nelson’s modified version [41],

in which the subject is given clear information about thechange in a rule at the time of its occurrence. The num-ber of categories subjects attained was recorded. Weapplied the same procedure to both Japanese and Britishparticipants. Instructions were given to Japanese sub-jects in Japanese.

2.2.4. The Stroop Colour Word Test (SCW)This consists of two tasks, in both of which subjects

are given a page with a series of 112 colour wordsprinted in different colours of ink. The number of cor-rect responses in the second task (Colour Word Task)is scored. A Japanese version with the same number ofcolour words printed in different colours was admin-istered to Japanese subjects. The colour words in theJapanese versions were similar in number of syllablesto their English counterparts.

2.2.5. Goal Neglect Test (GNT)In this test, a series of capital letters or numbers is

presented in the middle of a computer screen. Each trialconsists of 13 stimulus pairs (either letter or number


pairs) and begins with the word READY, which is re-placed by the instruction WATCH RIGHT or WATCHLEFT when the experimenter presses a key. A stimulussequence then begins, composed of the first 10 pairsand one + or − cue followed by the second three pairs.Subjects are given the task of naming the letters onthe side indicated by the first instruction, for the firstten pairs, and those indicated by the second side in-struction (SSI), according to the rule that the + symbolmeans ‘watch right’ and – ‘watch left’, for the last threepairs. Subjects make a block of twelve experimentaltrials consisting of six ‘stay’ trials (WATCH RIGHTfollowed by + and WATCH LEFT followed by −) andsix ‘switch’ trials (WATCH RIGHT followed by – andWATCH LEFT followed by +). The test is performedafter a few practice trials. Whether or not subjects re-sponds appropriately to the SSI is assessed. Japanesesubjects performed a Japanese version with Hiraganacharacters, instead of letters of the Roman alphabet.

2.2.6. Behavioural Assessment of DysexecutiveSyndrome (BADS)

This consists of six sub-tests. From each a ‘sum-mary profile score’ is obtained (with a maximum of 4and minimum of 0) and these are added up to producean overall score (out of 24). Compared with traditionaltests of EFs, this new battery has the advantage of ‘eco-logical validity’, i.e. its tasks are reflective of every-day cognitive contexts. We applied the same procedureto both Japanese and British participants, although in-struction to Japanese subjects was spoken in Japanese.We provide a brief explanation of the tests here, whilethe test manual shows more detailed descriptions.

2.2.6.1. Rule shift cardsThis test consists of ‘Trial 1’ and ‘2’, both of which

use the same set of 21 spiral-bound non-court playingcards, including both black and red cards which appearat random. Its purpose is to assess subjects’ ability toperform a given task procedure appropriately, to shiftfrom one rule to another, and to inhibit a pattern ofresponse learned immediately before the task is per-formed. In Trial 1 they are asked to say ‘Yes’ to a redcard and ‘No’ to a black card, as cards are turned overone by one. In Trial 2 they are asked to say ‘Yes’ if thecard is the same colour as the previous one, otherwiseto say No’.

2.2.6.2. Action programmeThis test aims to examine the development of an

action plan by the subject. They are given a rectangularstand into which a large plastic beaker and a thin tubeare placed. The beaker is two thirds full of water andcovered by a removable lid with a small central hole init. The tube includes a small piece of cork at the bottom.Both the beaker and the tube are transparent. Subjectsare asked to get the cork out of the tube, using any ofthe following materials: a metal, L-shaped rod which istoo short to reach the cork; a small screw-top container;and its unscrewed top. A stipulation is that subjects areforbidden to lift up the stand, the tube or the beaker orto touch the lid with their fingers. Subjects are requiredto identify and organise the following procedures: toremove the lid from the beaker, using the wire; to attachthe top to the small container and use this to take waterfrom the beaker and pour it into the tube in order tofloat the cork to the top.

2.2.6.3. Key searchSubjects are given a piece of paper in whose centre a

10 cm square is drawn with a small dot five cm belowit. They are asked to imagine that this square is a largefield and that somewhere in this field they have losttheir keys. The black dot denotes their starting point.Their task is to draw a line to show how the field canbe searched so that the keys will be found.

2.2.6.4. Temporal judgementThis test includes four questions which require sub-

jects to estimate the length of time required for certainactivities. They are told that they are not expected toanswer these questions precisely but that they shouldmake a sensible guess. The questions are: “How longdoes it take to have a routine dental check up?”; “Howlong does it take for a window cleaner to clean the win-dows of an average size house?”; “How long do mostdogs live for?”; and “How long does it take to blow upa party balloon? “.

2.2.6.5. Zoo mapThis test consists of two parts, both of which ask sub-

jects to show how they would visit designated placeson a map of a zoo without breaking the rule of usingdesignated paths once only. There are only four varia-tions on a route which conform to the rules. The firstpart of the test requires subjects to plan the order inwhich to visit the locations. The second part gives themexplicit instructions about how to plan a route in orderto avoid errors. Japanese subjects were given JapaneseZoo Maps in which all place names and relevant in-structions were written in Japanese.


2.2.6.6. Modified six elements testSubjects are set three tasks – dictation, arithmetic

and picture naming – each of which consists of PartsA and B, hence six sub-tasks in total. They must obeytwo rules. First, they have to attempt at least one thingfrom each of the six sub-tasks within ten minutes. Thatis, they must at least attempt each of the six sub-tasks.Second, they must not do two parts of the same task,oneafter the other. Japanese subjects were given a Japaneseinstruction sheet in which all instructions were writtenin Japanese.

2.3. Analyses

We used the SPSS V8 Package for descriptive andinferential statistical analysis. Analysis of covariance(ANCOVA), with adjustment for the effects of theRAPM-based general intelligence, was used to studyboth the main effects of condition (schizophrenic pa-tients versus control subjects) and nationality (Japaneseversus British), as well as their interactions, on rawscores of neuropsychological tests.

Where homogeneity of variance differed signifi-cantly between groups according to the Levene test, ad-ditional non-parametric analyses (Kruskal-Wallis tests)were performed on the variables. In fact, the Levenetest revealed significant differences of homogeneity ofvariance between groups on some of the measures, suchas the TMT, the SCW, the GNT and some sub-tests ofthe BADS. But non-parametric analyses did not alterthe main findings of these tests.

In Fig. 1, raw test scores were transformed to zscores based on the means and standard deviations ofthe British normal comparison group. The GNT wasexcluded from the analysis as its scores showed a bi-modal rather than normal distribution [13]. Where highscores indicated poorer performance,scores were trans-formed (direction reversed) so that high scores alwaysdenoted better cognitive performance.

3. Results

RAPM scores were submitted to a preliminary anal-ysis of variance (ANOVA) using two between-subjectfactors: clinical condition (schizophrenic patients ver-sus control subjects) and nationality (Japanese andBritish). The ANOVA revealed a significant main effectof condition (F = 30.746, df = 3, 68, p < 0.001).ANCOVA, which controlled for the RAPM-based cur-rent intelligence, revealed a significant main effect

of clinical condition on neuropsychological perfor-mance. Schizophrenic patients performed worse onmost conventional executive tests, including the TMT(F = 6.213, df = 1, 68, p = 0.015), the MCST(F = 7.482, df = 1, 60, p = 0.008), and theSCW (F = 8.780, df = 1, 66, p = 0.004). Anewly created computerised letter-monitoring test, theGNT, also revealed a significant inter-group differencein terms of clinical condition (F = 10.434, df =1, 54, p = 0.002). At the same time, a difference be-tween schizophrenic patients and control subjects onthe VFT did not reach the level of statistical significance(F = 0.008, df = 1, 68, p = 0.930). Schizophrenicpatients also scored worse on three sub-tests and theprofile score of the newly-devised comprehensive neu-ropsychological battery of EFs: the Rule Shift Cards(F = 4.115, df = 1, 65, p = 0.047); the Zoo Map(F = 9.390, df = 1, 66, p = 0.003); Modified Six El-ements (F = 8.955, df = 1, 65, p = 0.004); and theProfile score (F = 14.225, df = 1, 65, p < 0.001).Nationality as a main effect was not significant for anycognitive measures, except the GNT. The interactionof condition by nationality was not significant for anycognitive measures.

We further examined the relationship betweenEFs and general intellectual function by separatelyanalysing the performance of patients with minimalIQ decline. Based on Raven’s conversion table [45],RAPM raw scores for each schizophrenic subject wereconverted to normalised deviation IQ. Ten British pa-tients with a discrepancy of less than 15 points betweenNART estimated IQ and the RAPM current IQ werechosen. Basic variables in this group were as follows(means and, in parentheses, standard deviations): ed-ucation 12.2 (2.7); NART IQ 99.5 (12.0); RAPM IQ104.0 (12.4). Seven Japanese schizophrenic patientswith RAPM IQ equal to or higher than 90 were alsochosen. Basic variables in this group were as follows:education 12.5 (2.8); RAPM IQ 99.2 (13.2). As a testanalogous to the NART does not exist in the Japaneselanguage, it was not possible to estimate exactly pre-morbid intelligence in the Japanese patients. They werechosen, however, as the most intelligent amongst the18 Japanese patients on the basis of current IQs as in-dicated by RAPM scores. These two groups were, fi-nally, compared with the two control groups in termsof neuropsychological scores, using analysis of vari-ance (ANOVA) to study both the main effects of con-dition and nationality, as well as their interactions, onraw scores of neuropsychological tests. But, none ofthese re-computations changed the results very much(Table 5).


Table 4ANCOVA results upon neuropsychological results, using the RAPM score, as covariate, and two between-subjectfactors: condition (schizophrenic patients versus control subjects) and nationality (Japanese versus British)

Condition Nationality Condition × NationalityF P F P F P

VFT 0.008 0.930 0.741 0.392 0.191 0.663TMT B-A 6.213 0.015∗ 0.612 0.437 0.046 0.830MCST 7.482 0.008∗∗ 0.365 0.548 0.100 0.753SCW 8.787 0.004∗∗ 0.081 0.777 0.638 0.427GNT 10.434 0.002∗∗ 7.802 0.007∗∗ 0.542 0.465BADS Rule shift cards 4.115 0.047∗ 0.171 0.681 0.331 0.567

Action programme 3.028 0.087 0.069 0.793 0.253 0.617Key search 3.065 0.085 4.059 0.051 0.004 0.952Temporal judgement 3.016 0.087 3.603 0.062 1.881 0.175Zoo map 9.390 0.003∗∗ 2.374 0.103 3.342 0.072Modified six elements 8.955 0.004∗∗ 2.674 0.107 0.010 0.920Profile score 14.225 < 0.001∗∗ 2.713 0.104 0.113 0.738

∗p < 0.05; ∗∗p < 0.01.Note. VFT = Verbal Fluency Test [36]; TMT = Trail Making Test [47]; MCST = Modified Card Sorting Test [41];SCW = Stroop Colour Word Test [53]; GNT = Goal Neglect Test [14]; BADS = Behavioural Assessment ofDysexecutive Syndrome [57].

Table 5ANOVA results upon neuropsychological results for patients with preserved intelligence, using two between-subjectfactors: condition (schizophrenic patients versus control subjects) and nationality (Japanese versus British)

Condition Nationality Condition × NationalityF P F P F P

VFT 0.724 0.399 0.599 0.443 2.496 0.121TMT B-A 50.224 < 0.001∗∗ 10.884 0.002∗∗ 2.294 0.137MCST 21.894 < 0.001∗∗ 0.043 0.836 0.032 0.858SCW 27.762 < 0.001∗∗ 1.043 0.313 1.642 0.207GNT 24.587 < 0.001∗∗ 1.089 0.303 0.434 0.514BADS Rule shift cards 7.981 0.007∗∗ 0.156 0.694 0.020 0.888

Action programme 5.718 0.021∗ 2.390 0.129 0.949 0.335Key search 8.234 0.006∗∗ 5.087 0.029∗ 0.409 0.526Temporal judgement 4.032 0.049∗ 9.243 0.004∗∗ 0.101 0.752Zoo map 29.586 < 0.001∗∗ 0.123 0.727 0.145 0.706Modified six elements 7.988 0.007∗∗ 0.489 0.488 0.489 0.488Profile score 23.578 < 0.001 2.269 0.139 0.001 0.981

∗p < 0.05; ∗∗p < 0.01.Note. VFT = Verbal Fluency Test [36]; TMT = Trail Making Test [47]; MCST = Modified Card Sorting Test [41];SCW = Stroop Colour Word Test [53]; GNT = Goal Neglect Test [14]; BADS = Behavioural Assessment ofDysexecutive Syndrome [57].

In view of the potential influence of pharmacother-apy [12,34,36], the effect of drugs on neuropsycho-logical performance was analysed. In fact, 14 outof 22 British patients were taking clozapine amongother drugs, and 12 this medication alone, whereas theJapanese patients were taking haloperidol, levomepro-mazine, and chlorpromazine (clozapine is not yet au-thorised in Japan). Twelve British schizophrenic pa-tients on clozapine monotherapy were compared with10 Japanese patients on typical neuroleptics equalisedfor the averages of age, duration of education, durationof illness, and current intelligence indicated by RAPMscore. ANCOVA, using the RAPM score as covari-ate, did not reveal significant differences between the

British clozapine group and the Japanese traditionalneuroleptics group on any of the executive tests.

3.1. Summary of results

EFs in the Japanese sample were as impaired as inthe British one. Irrespective of nationality, the deficitsin EFs, as assessed by most executive tests, were moresevere than the deficits in RAPM-based intelligence. Inboth clinical samples, there was a severe impairment onformal executive tests, such as the TMT, the MCST, theSCW, and the GNT, although performance on the VFTwas not significantly impaired. These groups also per-formed poorly on everyday executive tests. Impairment


was apparent on some sub-tests and the profile scoreof the BADS in the two schizophrenic groups. Thesame profile of impairment was found amongst sub-jects of both cultures with minimal intellectual deteri-oration. Type of neuroleptics did not seem to influencethe profile of impairment very much.

4. Discussion

4.1. Relationship of EFs to intelligence

These findings suggest that both intelligence andEFs, including everyday executive abilities, were af-fected regardless of culture. The z score profiles ofthe four groups on the neurobehavioural measures areplotted on Fig. 1. The mean of the British control groupis represented by the zero line, with SD = 1 for allfunctions. As Fig. 1 shows, there was a clear differencein performance pattern between the clinical groups andthe healthy comparison groups. Both clinical groupsmade poor performance on four of the five executivetests, and this seemed to be not necessarily related tothe level of intelligence of either group. For example,in the two schizophrenic groups, differences betweenthe RAPM on the one hand and the TMT, the MCSTand the BADS on the other were more than two stan-dard deviations away from the British control subjects,and between the RAPM and the SCW there was morethan one standard deviation. Contrary to expectation,both clinical groups performed less poorly on the VFTthan on the RAPM intelligence test. The same neu-ropsychological pattern was shared by both Japaneseand British schizophrenic patients.

RAPM-based intelligence in the two schizophrenicgroups was significantly lower than that in the twocontrol groups. The fact that the measurements ofthe British schizophrenic group were lower than thoseof the British control group in terms of the RAPM-based intelligence (post-hoc Tukey: p = 0.002) in spiteof matched NART-based premorbid intellectual levelmeant the intellectual decline in the former group whichcame about as a result of the onset of schizophrenia.Due to the absence of a test analogous to the NARTin the Japanese language, we could not exactly esti-mate premorbid intelligence in the Japanese patients.For this reason, the difference between the Japaneseschizophrenic and control groups in terms of the RAPMperformance (post-hoc Tukey: p = 0.001) did notnecessarily signify the intellectual deterioration in theJapanese schizophrenic patients.

The ANCOVA result suggested that it seemed to bedifficult to attribute executive deficits merely to that oflowered levels of intelligence. It is unfortunate that wecannot completely rule out the possibility that, beyonda certain level of decline, relatively small intellectualdecrements might be causally associated with largerdeficits in EFs in some non-linear fashion. Indeed, inorder to cope with this problem to some extent, we anal-ysed data from the minimal intellectual decline sub-groups. But, we grant that the hypothesis of psycho-metric independence of EFs from general intelligenceshould be tested on the basis of a much larger sampleof schizophrenic patients whose current intelligence ismatched with that of the control subjects.

At least, we may exclude the possibility that thefindings are attributed merely to the limited sensitiv-ity of the RAPM. Due to its relationship to ‘fluid in-telligence’, this test was chosen in preference to theWechsler Adult Intelligence Scale (WAIS) [55]. TheRAPM [46] consists of visual pattern matching andanalogy problems, pictured in abstract designs whichrequire the subject to perceive and discriminate spa-tial, design, and numerical relationships. Like Cattell’sCulture Fair [7], this test is intended to be a ‘culture-free’ test of general ability in that it requires neitherlanguage nor academic skills for success but, rather,reasoning and novel problem solving for which famil-iar solutions are not available [30]. In this respect, theRAPM shares the characteristics of ‘fluid intelligence’tests with Cattell’s Culture Fair.

Although we did not actually administer the WAISto the patients, it is unlikely that schizophrenic patientsin our sample would potentially have made a poor per-formance on the WAIS. This is in the light of the factthat the schizophrenic groups in our sample showedrelatively good performance on the VFT. Interestinglyenough, this fact contrasts sharply to the study of Craw-ford et al. [10] in which patients with schizophreniawere associated with significantly lower VFT scoresthan would be predicted on the basis of Verbal IQ scoresof the WAIS. Although, at first glance, the presentfindings of relatively well-preserved VFT performancecontradict the observation of Crawford et al., there maybe two implications; (1) the verbal IQ of schizophrenicpatients should have been, by no means, worse thanthat of the control subjects in the present study and (2)the patients might be associated with larger deficits in adomain of EFs that are not explained by the VFT but arenevertheless assessed by other executive tests such asthe TMT, the MCST, the SCW and the BADS. Be thatas it may, these results can be cautiously interpreted


Japanese Schizophrenia

British Schizophrenia

Japanese Controls

British Controls

1

0

-1

-2

-3

-4

-5

-6

-7

z S

core

NART RAPM VFT TMT MCST SCW BADS

Fig. 1. The profiles of impairment: the Japanese and British patients, the Japanese and British control subjects (standard deviations from meanof the British control group). Note. NART = National Adult Reading Test [42]; RAPM = Raven Advanced Progressive Matrices [46]; VFT =Verbal Fluency Test [36]; TMT = Trail Making Test [47]; MCST = Modified Card Sorting Test [41]; SCW = Stroop Colour Word Test [53];BADS = Behavioural Assessment of Dysexecutive Syndrome [57].

as suggesting that poor performance on executive testswas not entirely due to the impairment of intelligencerelating to all cognitive domains.

This interpretation of the data in terms of the rela-tionship between EFs and intellectual impairment inschizophrenia is consistent with the following find-ings. Applying the neuropsychological case-study ap-proach to five chronic schizophrenic subjects, Shalliceet al. [51] revealed ubiquitous impairment in perfor-mance on tests sensitive to frontal executive deficits.Using the BADS, Evans et al. [17] reported that signifi-cant impairment continued to be found in patients withchronic schizophrenia even after those with remark-able decline in general intellectual functioning had beenexcluded. Elliott et al. [15] compared schizophrenicand control subjects on a computerised test of at-tentional set-shifting. Chronic schizophrenic patientswere found to experience significant difficulty in shift-ing to a novel dimension and ignoring the previouslyrelevant one, and this was equally true of a sub-sampleof patients with preserved IQ.

These findings suggest that the disturbance ofintegration and organisation of behaviour seen inschizophrenia may be related to dysfunction in thefrontal cortex and its allied structures. Although otherlocalising hypotheses cannot be ruled out, they haveless empirical support. A considerable body of evi-dence has accumulated in favour of a close associa-tion between frontal lobe damage and impaired perfor-mance on executive tests [9,44,48].

4.2. Cross-cultural similarities of schizophrenia

Our study also shows that in spite of major cul-tural differences, Japanese and British schizophrenicpatients do not differ much in regard to their dysex-ecutive profile. Indeed, we should admit that the the-matic content of some positive symptoms may be con-ditioned by culture. As for symptomatology, all we cansay is at best that no prominent difference was foundbetween the two schizophrenic groups in terms of pos-itive syndrome, negative syndrome, anergia, thoughtdisturbance, hyperactivation, paranoid and belligerenttendency, and depression (Table 2). These findingssupport the view of WHO (1979) that a class of com-mon core symptoms universally underlies schizophre-nia. However, the thematic aspect of psychopathol-ogy could not be verified, as the Positive and NegativeSyndrome Scale (PANSS) [25] is only concerned withthe form and severity of symptoms. It is also true thatsocial factors in the development of cognitive abilitiesmust be allowed for. Even so, it would seem that thebasic neuropsychological disturbance of schizophreniaaffects cognitive domains less influenced by culturalvariation.

However, the finding that there is no statistically sig-nificant difference between the Japanese and the Britishsamples, does not guarantee that no difference wouldever be found if a larger sample or other instrumentswere to be used. Even so, the issue of the power ofstatistical analysis should not be allowed to obscurethe main thrust of our study for the following reason.The purpose of this study was to specify the ‘dysexec-


utive syndrome’ in Japanese schizophrenic patients asa stable ‘syndrome’. Here, the term syndrome means aunique constellation of signs and symptoms which oc-cur together frequently enough to suggest an underly-ing disease process [54]. Its central connotation is thatthe signs and symptoms occur with each other muchmore often than each of them arising separately, to-gether with other signs and symptoms. Our current in-terest, therefore, lies in the simultaneous appearance ofa constellation of neuropsychological findings specificto DES in Japanese as well as British patients. Thus,we emphasise the concurrence of lowered scores on anumber of executive tests, with intelligence relativelyunimpaired.

The finding of similar neuropsychological abnormal-ities in patients with schizophrenia from different cul-tures may possibly support the view that this conditionhas a biological basis and that it is present in variouscultures. Such cultural ubiquity is also observed inanti-saccadic eye movement [1] and N400 event-relatedpotential [5]. The cross-cultural stability of neurobi-ological data obtained by different methods contrastsmarkedly with the finding that socio-cultural variablesare significant mediators of cross-ethnic symptom dif-ferences [6]. The above evidence refutes the extremecultural-relativistic view of schizophrenia and supportsMurphy’s [38] view: “(r)ather than being simply vio-lations of the social norms of particular groups, as la-belling theory suggests, symptoms of mental illness aremanifestations of a type of affliction shared by virtuallyall mankind.”

4.3. Cross-cultural applicability of the ‘ecologicallyvalid’ test

The ecological validity of the BADS, which was de-vised to measure everyday executive problems [57],does not seem to interfere with its cross-cultural ap-plicability very much. The requirements of each sub-task are similar to those of real-life activity, and, con-sequently, reflect the daily demands of the culture inwhich the BADS was devised. Still, no significantdifference was found in test performances betweenJapanese and British schizophrenic patients, suggest-ing that the BADS can be applied equally to Japanesesubjects, and, perhaps even individuals of other nation-alities.

4.4. Application of neuropsychological assessment toclinical practice in a multi-ethnic society

Because the neuropsychological assessment of oursamples was resistant to socio-cultural variables, it canbe deduced that neuropsychological assessment in gen-eral should be considered useful in the severity assess-ment, outcome prediction and the management and re-habilitation of patients with schizophrenia in a multi-ethnic milieu.

Clinical decision is at present still determined bydescriptive information provided by subjects withschizophrenia and by their care-givers [2,59]. The cen-tral weakness of this approach is its susceptibility tosocio-cultural factors [29].

In this respect, neuropsychological assessment cansupplement subjective-phenomenological data. Whilewe found a quantitative concordance between Japaneseand British patients on a wide range of frontal execu-tive tests, we also observed common examination be-haviour in schizophrenic patients with DES, irrespec-tive of nationality. When qualitative aspects of aberrantbehaviour as well as numerical evidence are appropri-ately analysed, psychometric instruments may provideadded clinical information relevant to the understand-ing and management of schizophrenic patients.

5. Conclusion

This study revealed that both British and Japanesegroups of schizophrenic patients showed equally severeimpairment in the BADS as well as conventional execu-tive tests (although verbal fluency and intelligence wereless impaired). It is unlikely that poor performance onexecutive tests was due entirely to the impairment ofintelligence relating to all cognitive domains. This isbecause similar neuropsychological deficits were alsofound in patients with minimal intellectual deteriora-tion, irrespective of cultural origin. These findings sug-gested that socio-cultural background does not affectthe dysexecutive profile of schizophrenia very much,and that neuropsychological assessment may possiblyprovide added clinical information relevant to the man-agement and rehabilitation of schizophrenic patientsacross different cultures.

Acknowledgements

We thank all staff members of the Cambridge Psychi-atric Rehabilitation Service, Muroi Hospital, Oyama


Fujimidai Hospital, and Nasu Hillside Hospital whoallowed us to examine patients under their care. Weare also grateful to Professors Eric Chen for commentsupon earlier drafts of this paper. We have received noexternal funding for this research.

References

[1] J.S. Allen, A.J. Lambert, F.Y. Johnson, K. Schmidt and K.L.Nero, Antisaccadic eye movements and attentional asymme-try in schizophrenia in three Pacific populations, Acta Psychi-atrica Scandinavica 94 (1996), 258–265.

[2] American Psychiatric Association, Diagnostic and StatisticalManual of Mental Disorders: Fourth Edition, American Psy-chiatric Association, Washington, DC, 1994.

[3] A.D. Baddeley, Working Memory, Oxford University Press,Oxford, 1986.

[4] F.M. Benes, I. Sorensen, S.L. Vincent, E.D. Bird and M.Sathi, Increased density of glutamate-immunoreactive verti-cal processes in superficial laminae in cingulate cortex ofschizophrenic brain, Cortex 2 (1992), 503–512.

[5] M.A. Bobes, Z.X. Lei, S. Ibanez, H. Yi and M. Valdes-Sosa,Semantic matching of pictures in schizophrenia: a cross-cultural ERP study, Biological Psychiatry 40 (1996), 189–202.

[6] J.S. Brekke and C. Barrio, Cross-ethnic symptom differencesin schizophrenia: the influence of culture and minority status,Schizophrenia Bulletin 23 (1997), 305–316.

[7] R.B. Cattell and A.K.S. Cattell, Test of ‘g’: Culture Fair,Institute for Personality and Ability Testing, Champaign, IL,1973.

[8] R. Chandrasena, Schneider’s First Rank Symptoms: An inter-national and interethnic comparative study, Acta PsychiatricaScandinavica 76 (1987), 574–578.

[9] J.R. Crawford, ed., Assessment of Attention and ExecutiveFunctions, Neuropsychological Rehabilitation 8 (1998), Spe-cial Issue.

[10] J.R. Crawford, M.C. Obonswain and M. Bremner, Frontallobe impairment in schizophrenia: relationship to intellectualfunctioning, Psychological Medicine 23 (1993), 787–790.

[11] J.M. Davis, Comparative dose and cost of antipsychotic med-ication, Archives of General Psychiatry 33 (1976), 858–861.

[12] A.Y. Deutch, Mechanisms of action of clozapine in thetreatment of neuroloptic-resistant and neuroleptic-intolerantschizophrenia, European Psychiatry 10 (1995), 39–46.

[13] J. Duncan, Attention, intelligence, and the frontal lobes,in: The Cognitive Neurosciences, M.S. Gazzaniga, ed., MITPress, Cambridge, MA, 1995, pp. 721–733.

[14] J. Duncan, H. Emslie, P. Williams, R. Johnson and C. Freer,Intelligence and the frontal lobe: The organization of Goal-directed behavior, Cognitive Psychology 30 (1996), 257–303.

[15] R. Elliott, P.J. McKenna, T.W. Robbins and B.J. Sahakian,Neuropsychological evidence for frontostriatal dysfunction inschizophrenia, Psychological Medicine 25 (1995), 619–630.

[16] J.B. Enright and W.R. Jaeckle, Psychiatric symptoms and di-agnosis in two subcultures, International Journal of SocialPsychiatry 9 (1963), 12–17.

[17] J.J. Evans, S.E. Chua, P.J. McKenna and B.A. Wilson, Assess-ment of the Dysexecutive syndrome in schizophrenia, Psycho-logical Medicine 27 (1997), 635–646.

[18] C.D. Frith, The Cognitive Neuropsychology of Schizophrenia,Lawrence Erlbaum Associates, Hove, 1992.

[19] E. Goldberg, Akinesia, tardive dysmentia, and frontal lobedisorders in schizophrenia, Schizophrenia Bulletin 11 (1995),255–263.

[20] T.E. Goldberg, J.R. Kelsoe, D.R. Weinberger, N.H. Pliskin,P.D. Kirwin and K.F. Berman, Performance of schizophrenicpatients on putative neuropsychological tests of frontal lobefunction, International Journal of Neuroscience 42 (1988),51–58.

[21] R.S. Goldman, B.N. Axelrod, R. Tandon and S. Bernet, Anal-ysis of executive functioning in schizophrenics using the Wis-consin Card Sorting Test, Journal of Nervous and Mental Dis-eases 179 (1991), 507–508.

[22] T. Hatta and S.J. Dimond, Comparison of lateral differencesfor digit and random-form recognition in Japanese and West-erners, Journal of Experimental Psychology, Human Percep-tual Performance 6 (1980), 174–368.

[23] A.R. Jensen, Bias in Mental Testing, Methuen & Co., London,1980.

[24] M.M. Katz, K.O. Sanborn, H.A. Lowery and J. Ching, Ethnicstudies in Hawaii: Psychopathology and social deviance, in:The Nature of Schizophrenia, L. Wynne, R.L. Cromwell andS. Matthysse, eds, John Wiley & Sons, Inc., New York, 1978,pp. 572–584.

[25] S.R. Kay, A. Opler and A. Fiszbein, Positive and NegativeSyndrome Scale (PANSS) Manua, Multi-Health Systems Inc.,Toronto, 1990.

[26] D.J. King, Neuroleptics and the treatment of schizophrenia,in: Seminars in Clinical Psychopharmacology, D.J. King, ed.,Gaskell, London, 1995, pp. 259–327.

[27] B. Kolb and I.Q. Whishaw, Performance of schizophrenic pa-tients on tests sensitive to left or right frontal, temporal orparietal function in neurological patients, Journal of Nervousand Mental Disease 171 (1983), 435–443.

[28] E. Kraepelin, Vergleichende Psychiatrie, Zentralblatt fur Ner-venheilkunde und Psychiatrie 15 (1904), 433–437.

[29] J. Leff, International variations in the diagnosis of psychiatricillness, British Journal of Psychiatry 131 (1977), 329–338.

[30] M.D. Lezak, Neuropsychological Assessment: Third Edition,Oxford University Press, Oxford, 1995.

[31] P.F. Liddle and D.L. Morris, Schizophrenic symptoms andfrontal lobe performance, British Journal of Psychiatry 158(1991), 340–345.

[32] K.M. Lin and A.M. Kleinman, Psychopathology and clin-ical course of schizophrenia: A cross-cultural perspective,Schizophrenia Bulletin 14 (1988), 555–567.

[33] R.E. Litman, D.W. Hommer, T. Clem, M.L. Ornsteen, C. Olloand D. Pickar, Correlation of Wisconsin Card Sorting Testperformance with eye tracking in schizophrenia, AmericanJournal of Psychiatry 148 (1991), 1580–1582.

[34] H.Y. Meltzer, Dimensions of outcome with clozapine, BritishJournal of Psychiatry 160 (1992), 46–53.

[35] E. Miller, Verbal fluency as a function of a measure of ver-bal intelligence and in relation to different types of cerebralpathology, British Journal of Clinical Psychology 23 (1984),53–57.

[36] A.M. Mortimer, Cognitive function in schizophrenia: Do neu-roleptics make a difference? Pharmacology, Biochemistry andBehavior 56 (1997), 789–795.

[37] E.M. Moss, R.J. Davidson and C. Saron, Cross-cultural differ-ences in hemisphericity: EEG asymmetry discriminates be-tween Japanese and Westerners, Neuropsychologia 23 (1985),131–135.

[38] J.M. Murphy, Psychiatric labeling in cross-cultural perspec-tive, Science 191 (1976), 1019–1028.


[39] H.B.N. Murphy, Culture and schizophrenia, in: Culture andPsychopathology, I. Al-Issa, ed., University Park Press, Balti-more, 1982, pp. 221–249.

[40] H.B.M. Murphy, E.D. Wittkower, J. Fried and H. Ellenberger,A cross-cultural survey of schizophrenic symptomatology, In-ternational Journal of Social Psychiatry 9 (1963), 237–249.

[41] H.E. Nelson, A modified card sorting task sensitive to frontallobe defects, Cortex 12 (1976), 313–324.

[42] H. Nelson and J.R. Willison, The National Adult Reading Test(NART), (2nd ed.), NFER-Nelson, Windsor, 1991.

[43] C. Pantelis, T.R.E. Barnes and H.E. Nelson, Is the con-cept of frontal-subcortical dementia relevant to schizophrenia?British Journal of Psychiatry 160 (1992), 442–460.

[44] P. Rabbitt, ed., Methodology of Frontal and Executive Func-tion, Psychology Press, Hove, 1997.

[45] J.C. Raven, Advanced Progressive Matrices: Set I, OxfordPsychologists Press, Oxford, 1962.

[46] J.C. Raven, Advanced Progressive Matrices, Oxford Psychol-ogists Press, Oxford, 1976.

[47] R.M. Reitan, Validity of the trail-making test as an indicationof organic brain damage, Perceptual and Motor Skills 8 (1958),271–276.

[48] A.C. Roberts, T.W. Robbins and L. Weiskrantz, eds, The Pre-frontal Cortex: Executive and Cognitive Functions, OxfordUniversity Press, Oxford, 1998.

[49] C. Schooler and W. Caudill, Symptomatology in Japanese andAmerican schizophrenics, Ethnolog 3 (1964), 172–178.

[50] J. Schroder, F. Wenz, L.R. Schad, K. Baudendistel and M.V.Knopp, Sensorimotor cortex and supplementary motor areachanges in schizophrenia: a study with functional magneticresonance imaging, British Journal of Psychiatry 167 (1995),197–201.

[51] T. Shallice, P.W. Burgess and C.D. Frith, Can the neuropsy-chological case-study approach be applied to schizophrenia?Psychological Medicine 21 (1991), 661–673.

[52] D. Tamlyn, P.J. McKenna, A.M. Mortimer, C.E. Lund,S. Hammond and A.D. Baddeley, Memory impairment inschizophrenia: its extent, affiliations and neuropsychologicalcharacter, Psychological Medicine 22 (1992), 101–115.

[53] M.R. Trenerry, B. Crosson, J. DeBoe and W.R. Leber, StroopNeuropsychological Screening Test Manual, PsychologicalAssessment Resources, Odessa, 1989.

[54] K.W. Walsh, Understanding Brain Damage. A Primer of Neu-ropsychological Evaluation. Second Edition, Churchill Liv-ingstone, Inc., London, 1991.

[55] D. Wechsler, Wechsler Memory Scale-Revised Manual, ThePsychological Cooperation, San Antonil Tx, 1987.

[56] D.R. Weinberger, K.F. Berman and B.P. Illowsky, Physiologi-cal dysfunction of dorsolateral prefrontal cortex in schizophre-nia. III. A new cohort and evidence for a nomoanimergic mech-anism, Archives of General Psychiatry 45 (1988), 609–615.

[57] B.A. Wilson, N. Alderman, P. Burgess, H. Emslie and J.J.Evans, Behavioural Assessment of the Dysexecutive Syndrome(BADS), Thames Valley Test Company, Bury St. Edmunds,1996.

[58] World Health Organization, Schizophrenia: An InternationalFollow-up Study, Wiley, New York, 1979.

[59] World Health Organization, The ICD-10 Classification ofMental and Behavioural Disorders: Clinical Descriptions andDiagnostic Guideline, World Health Organization, Geneva,1992.

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Dysexecutive syndrome in schizophrenia: A cross-cultural